Ordinary female college student Luna, in order to raise money for her younger brother's brain tumor surgery, accidentally enters the dark web's black market and is bought by the Ashford brothers, a demonic bloodline family that has existed for six hundred years, for a high price of five million. Damien, Raven, and Knox each have uncontrollable demon genes sealed within them, which gradually turn them into beasts during the blood moon. Only Luna, with her naturally high body temperature and angelic bloodline, can suppress the restless beast marks inside them. Forced to stay in the manor, Luna accompanies the brothers to gain a chance to save her brother while investigating the whereabouts of her mother who disappeared twenty-two years ago. She unexpectedly discovers that she is the ultimate anchor of angel-demon hybrid blood and the only one who can completely lift the brothers' curse, although the permanent purification ritual will drain all her life force. On the other hand, Serena, heir of the rival Voss family, sees Luna as a mortal enemy, repeatedly setting traps, orchestrating abductions, and sowing discord in an attempt to seize or eliminate her. As Luna searches for her biological father and uncovers the long-hidden secrets of her family, she develops bonds with the three brothers, who carry painful pasts. On the eve of the blood moon, Serena sets a deadly trap to corner them. To protect the three brothers and her loved ones, Luna risks her own bloodline power to initiate the purification ritual, sparking a life-and-death battle concerning curses, family, and mutual redemption.
